Related Experiment Video
Updated: Aug 23, 2026
Conjunctival Commensal Isolation and Identification in Mice
Published on: May 1, 2021
Susceptibility testing of Streptococcus mitis group isolates
G Bancescu1, S Dumitriu, A Bancescu
1Chair of Microbiology, University of Medicine & Pharmacy "Carol Davila", Romania.
Background & Objectives:
Suppurative oral and maxillofacial infections are usually mixed infections due to aerobic and anaerobic bacteria, most frequently by oral streptococci and antimicrobial treatment is necessary for such infections. The aim of this study was to investigate the antimicrobial susceptibility of Streptococcus mitis group strains isolated from Romanian patients with different oral and maxillofacial infections.
Methods:
Eighty-five isolates belonging to S. mitis group isolated from pus samples were identified at species level by the Rapid ID 32 STREP system. The E test was used to determine the susceptibilities of the isolates to penicillin, ampicillin, cefotaxime, erythromycin, clindamycin, chloramphenicol and tetracycline.
Results:
Of the 151 samples studied, 85 isolates belonged to S. mitis group. The minimum inhibitory concentration (MIC) values (mg/l) ranged from 0.016-0.75 for penicillin, 0.016-2 for ampicillin, 0.016- 1 for cefotaxime, 0.016-4 for erythromycin, 0.016-0.047 for clindamycin, 0.5-4 for chloramphenicol and 0.047-256 for tetracycline.
Interpretation & Conclusion:
The low susceptibility and the resistance to some commonly used antibiotics found in this study indicated a need for a careful surveillance of the susceptibility pattern of oral streptococci isolates of clinical significance. Clindamycin and chloramphenicol might be suitable alternative agents in treatment of oral and maxillofacial infections involving penicillin-resistant bacteria and in case of patients with hypersensitivity to beta-lactam antibiotics.
Insights
Antimicrobial susceptibility testing of oral streptococci in Romania revealed resistance to common antibiotics. Clindamycin and chloramphenicol show promise for treating oral infections caused by resistant bacteria.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Suppurative oral and maxillofacial infections are often polymicrobial, involving aerobic and anaerobic bacteria, with oral streptococci being frequent culprits.
- Effective antimicrobial treatment is crucial for managing these infections, necessitating an understanding of bacterial susceptibility patterns.
Purpose of the Study:
- To investigate the antimicrobial susceptibility profiles of Streptococcus mitis group strains.
- To analyze isolates from Romanian patients diagnosed with various oral and maxillofacial infections.
Main Methods:
- Identification of 85 Streptococcus mitis group isolates from 151 pus samples using the Rapid ID 32 STREP system.
- Determination of minimum inhibitory concentrations (MICs) via E test for penicillin, ampicillin, cefotaxime, erythromycin, clindamycin, chloramphenicol, and tetracycline.
Main Results:
- MIC values for penicillin ranged from 0.016-0.75 mg/l, ampicillin 0.016-2 mg/l, cefotaxime 0.016-1 mg/l, erythromycin 0.016-4 mg/l, clindamycin 0.016-0.047 mg/l, chloramphenicol 0.5-4 mg/l, and tetracycline 0.047-256 mg/l.
- Significant variation in susceptibility was observed across the tested antibiotics, with notable resistance patterns.
Conclusions:
- The study highlights a concerning low susceptibility and resistance to commonly used antibiotics among oral streptococci isolates.
- Continuous surveillance of antibiotic susceptibility is essential for guiding effective clinical treatment strategies.
- Clindamycin and chloramphenicol emerge as potential alternative agents for treating oral and maxillofacial infections, particularly those involving penicillin-resistant strains or in patients with beta-lactam hypersensitivity.
